Biosimilar Trastuzumab for HER2-Positive Breast Cancer

The promise of biosimilar therapeutic and supportive agents in oncology offers the possibility of less expensive drugs that are equivalent in efficacy and safety to their reference products. Several biosimilars for trastuzumab are in development, and one (Mylan/Biocon MYL-1401O or trastuzumab-dkst) was recently FDA-approved to treat patients with HER2-positive breast cancer.

To test the efficacy, safety, and immunogenicity of another trastuzumab biosimilar agent (SB3; Samsung Bioepis), investigators conducted an industry-sponsored, randomized, double-blind, phase III study of 800 patients with stage II/III, HER2-positive, primary breast cancer who received neoadjuvant docetaxel followed by 5-fluorouracil, epirubicin, and cyclophosphamide plus either SB3 or reference trastuzumab (TRZ). Eligible patients had inflammatory disease, tumor size ≥2 cm, and confirmed diagnosis of infiltrating duct carcinoma. After surgery, patients completed 1 year of SB3 or TRZ.

The breast pathologic complete remission rate (the primary endpoint) was equivalent with SB3 or TRZ (51.7% and 42.0%, respectively). The pathologic complete response rate was 96.3% with SB3 and 91.2% with TRZ. Toxicity was similar with either agent.